The invention relates generally to diagnostic imaging and, more particularly, to an integrated scintillator and collimator and method of manufacturing same.
Typically, in computed tomography (CT) imaging systems, an x-ray source emits a fan-shaped beam toward a subject or object, such as a patient or a piece of luggage. Hereinafter, the terms “subject” and “object” shall include anything capable of being imaged. The beam, after being attenuated by the subject, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is typically dependent upon the attenuation of the x-ray beam by the subject. Each detector element of the detector array produces a separate electrical signal indicative of the attenuated beam received by each detector element. The electrical signals are transmitted to a data processing system for analysis which ultimately produces an image.
Generally, the x-ray source and the detector array are rotated about the gantry within an imaging plane and around the subject. X-ray sources typically include x-ray tubes, which emit the x-ray beam at a focal point. X-ray detectors typically include a collimator for collimating x-ray beams received at the detector, a scintillator for converting x-rays to light energy adjacent the collimator, and photodiodes for receiving the light energy from the adjacent scintillator and producing electrical signals therefrom.
As stated above, typical x-ray detectors include a collimator for collimating x-ray beams such that collection of scattered x-rays is minimized. As such, the collimators operate to attenuate off-angle scattered x-rays from being detected by a scintillator cell. Reducing this scattering reduces noise in the signal and improves the final reconstructed image. Therefore, it is necessary that the scintillator array and the collimator, typically plates extending along one dimension above the scintillator array, are precisely and uniformly aligned. That is, exact mechanical alignment is required between the collimator plates and the cast reflector lines in the array of scintillators.
To accomplish this, known manufacturing processes attempt this exact alignment by constructing a continuous collimator that is sized to dimensionally match the width and length of the entire detector array. That is, the collimator plates are arranged or arrayed in a continuous consistent pattern or pitch that spans the entire detector length and is placed and attached to the detector rail structure. As such, individual scintillator arrays or packs are must then be exactly aligned to the continuous collimator to ensure that all scintillator cells and collimator cells are aligned exactly; otherwise the collimator must be discarded or repaired, or the scintillator packs must be discarded. This process requires excessively tight tolerancing and requires great operator skill and patience to manually assemble the collimators to the scintillators to form the detector. Accordingly, these known processes are susceptible to waste of parts, material, and labor. Further, as the problem of the alignment of the collimator between the x-ray focal spot and the individual detector components currently is addressed only by maintaining tight tolerances in the hand assembled collimator/scintillator structures, the preservation of tight tolerances during the assembly process causes a great deal of cost and low yield during image quality testing of the resulting structures.
Additionally, as CT detectors grow in the z-direction, alignment requirements will tighten and the number of cells requiring alignment will increase. Therefore, the low process yields and high-end process scrap and re-work associated with these known manufacturing processes will increase the cost and time associated with CT detector assembly.
Therefore, it would be desirable to design an integrated scintillator and collimator assembly that includes precise alignment of the components as well as a method of manufacturing such an integrated scintillator and collimator that reduces the time and cost to provide the precisely aligned components.